Class Work

Collect Stream result

• Collecting stream result is terminal operation.
• Object[] toArrray()
• R collect(Collector)
  • Collectors.toList(), Collectors.toSet(), Collectors.toCollection(), Collectors.joining()
  • Collectors.toMap(key, value)

Stream of primitive types

• Efficient in terms of storage and processing. No auto-boxing and unboxing is done.
• IntStream class
  • IntStream.of() or IntStream.range() or IntStream.rangeClosed() or Random.ints()
  • sum(), min(), max(), average(), summaryStatistics()

Method references

• If lambda expression involves single method call, it can be shortened by using method reference.
• Method references are converted into instances of functional interfaces.
• Method reference can be used for class static method, class non-static method, object non-static method or constructor.

Examples

• Class static method: Integer::sum [ (a,b) -> Integer.sum(a,b) ]
  • Both lambda param passed to static function explicitly
• Class non-static method: String::compareTo [ (a,b) -> a.compareTo(b) ]
  • First lambda param become implicit param (this) of the function and second is passed explicitly (as arguments).
• Object non-static method: System.out::println [ x -> System.out.println(x) ]
  • Lambda param is passed to function explicitly.
• Constructor: Date::new [ () -> new Date() ]
  • Lambda param is passed to constructor explicitly.

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